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Multiscale modeling of physical and chemical processes

Team Leader Prof. Kovalev V.L.

Development of new science-intensive industrial sectors requires new studies of physicochemical processes under extreme conditions as well as design of new materials. Predictive modeling at an atomic-molecular level has recently become particularly relevant for such studies. The use of such modeling is nowadays possible due to rapid progress in modern supercomputer technologies.

The present scientific direction is focused on multi-disciplinary basic research of phenomena and processes, including construction of new multiscale models, development of new computing algorithms for their investigation and carrying out calculations with the use of multinuclear massively-parallel computational systems. The general mathematical approaches and cooperation of specialists in mechanics, mathematics and quantum chemistry make possible to investigate urgent applied problems of various physicomechanical nature on different spatial and time scales.

One of the numerous problems here (in this scientific direction) is connected with multiscale modeling of gas and fluid currents at catalytic surfaces. It includes currents in channels and pores of sorption and catalytic materials taking in account molecular structure as well as topological and structural material peculiarities.

Zeolites are molecular sieves

The analysis of interaction of gas phase molecules with different material surfaces is also used in rarefied gas aerodynamics problems which are of scientific and practical interest in various aerospace technologies. In addition, the investigations of catalytic properties of reusable spacecrafts heat-shielding coverings remain urgent because catalytic processes give more than half of the heat flux to the craft surface in hypersonic flow.

New materials, including nanostructured heat-shielding materials, are being developed for perspective hypersound aircrafts. Such materials should provide thermal protection at surface temperatures above 2000 K. The most recent approaches based on quantum mechanics and molecular dynamics can help to understand the mechanism of heterogeneous catalytic processes, analyze their elementary stages and estimate the influence of spatial structure of surface-layer on catalytic phenomena. To find a mechanism of heat-transfer processes and determine their key features is an important task for construction of more effective thermal protections. The theoretical description also allows to reduce the amount of experimental work necessary for reliable description of heterogeneous catalytic processes on spacecrafts surface.

At present the interest to such currents is constantly increasing due to development of micro- and nano-technologies. In particular, the use of new porous materials in catalytic and sorption processes and in electrotechnical devices makes it necessary the establishment of quantitative relations between chemical composition and material structure and functional characteristic expected from it. Accurate account of these factors is also necessary in order to define interaction laws between gas and surface in major perspective processes such as catalytic organic synthesis in meso- and nanoporous materials, processes passing in catalytic afterburners based on active nanoparticles, etc. Such analysis requires further improvement of models combining various spatial and time scales, but allows to conduct directed search and design of materials with given set of functional characteristics.

Moreover, modern technologies have opened up possibilities for manufacturing various micro- and nano-electromechanical systems (MEMS/NEMS) with unique characteristics such as light (insignificant) weight, low energy/power consumption, high efficiency and sensitivity. Designing a large quantity of similar devices is connected with such problems as gas and liquid current, heat transfer processes in micro and nano-structures. Methods of multiscale modeling of currents and physicochemical interactions in micro- and nano-structures and devices taking into account atomic structure of rigid body, chemical properties of gas, thermal motion of atoms on surface, adsorption phenomena, surface roughness and system macro geometry are being developed within the framework of this scientific direction.

Particularly, the possibilities of effective storage of hydrogen are investigated. It is important to notice that hydrogen is the most energetically effective and non-polluting gas.

The creation of multilevel models and corresponding program modules for investigating burning processes in combustion chambers and nonequlibrium currents in aviation engine gas turbines is one of the major fundamental problems in this scientific area. The kinetic schemes presenting gross reaction in terms of a set of elementary stages and reliable estimation methods of kinetic characteristics (speed factors, products distribution of elementary stages) are developed.

The corresponding algorithms are created for kinetic models verification and optimization of aviation engines work. Additionally, calculations of three-dimensional nonequilibrium currents in aviation engines basic knots are carried out.